FIG. 26 shows a cross-sectional view of a general optical fiber cored line 3 as an optical fiber. As shown in the same drawing, the optical fiber cored line 3 has a bare optical fiber 4, the outer diameter of which is approximately 125 .mu.m, formed with a clad 9 around the core 8, wherein the bare optical fiber 4 is further covered with a primary coat 15 and a nylon jacket 10, etc. still further covers the outer circumference thereof. The outer diameter of the optical fiber cored line 3 is, for example approximately 250 .mu.m, which is formed to be almost two times the outer diameter of the bare optical fiber 4.
A multiple-core optical connector has been widely used as an optical fiber connecting member by which a plurality of such optical fiber cored lines 3 are collectively connected. FIG. 27 shows an example of a conventional multiple-core optical connector. In the same drawing, an optical fiber tape 6 which is composed by juxtaposing a plurality (four in the drawing) of optical fiber cored lines 3 so as to be band-like is inserted into and fixed in a ferrule 2 used as an optical fiber arraying member, thereby forming a multiple-core optical connector, wherein the optical fiber cored lines 3 of the optical fiber tape 6 are inserted into the ferrule 2 in such a state where coatings, such as nylon jacket 10 and primary coat 15 (FIG. 26), located at the tip ends thereof are eliminated, and they are arrayed at an appointed array pitch so that the end faces of the bare optical fibers 4 which are exposed by eliminating the coatings are exposed to the connection end face 5 of the ferrule.
Furthermore, the ferrule 2 is usually formed by molding resin, etc., and, at the connection end face 51 a plurality (four in the drawing) of bores or grooves, such as optical fiber insertion holes 13, etc., for arraying the bare optical fibers 4 at an appointed pitch are disposed with a spacing at a pitch which is two times the outer diameter of the bare optical fibers 4, wherein by inserting the bare optical fibers 4 into the optical insertion holes 13, the bare optical fibers 4 may be disposed at a pitch (2 r) which is equal to two times the outer diameter (r) of the bare optical fibers 4.
However, recently, it becomes possible to carry out not only mutual connections of optical fiber cored lines 3 but also connections of waveguide elements, in which a plurality of optical waveguides are incorporated, with multiple-core optical connectors by connecting optical connectors to each other. Therefore, optical connectors in which more optical fiber cored lines 3 such as eight-core (8-core), sixteen-core (16-core), etc. are incorporated has been developing in compliance with a circuit configuration of waveguide elements. Furthermore, in line with high concentration of optical communications, multiple-core optical connectors, in which much more optical fiber cored lines such as thirty-two cores, sixty-four cores, etc. are incorporated, are desired for the purpose of high concentration.
Actually however, with a conventional multiple-core optical connector as shown in FIG. 27, the arraying pitch of bare optical fibers 4 of an optical fiber cored line 3 is formed to be approximately two times (for example, approximately 250 .mu.m) the outer diameter of the bare optical fibers 4. Therefore, in a case where it is assumed that the width of the marginal allowance B for reinforcement at both sides of the optical fiber arraying area is 1,000 .mu.m, in a multiple-core optical fiber connector of four cores as shown in FIG. 27, the element width thereof will be 3 mm (250 .mu.m.times.the number of cores+1,000 .mu.m.times.2), and as regards a multiple-core optical fiber connector of eight cores, the element width thereof will be 4 mm. Furthermore, the element width will be 6 mm for sixteen cores, 10 mm for thirty-two cores, and 18 mm for sixty-four cores, respectively.
Thus, the dimension of a multiple-core optical fiber connector is made remarkably large in line with an increase of the number of cores of optical fiber cored line 3 to be arrayed on a multiple-core optical connector. Therefore, there is a problem that, in a case where a multiple-core optical connector having many cores is produced, the number of production of waveguide elements in a wafer is remarkably decreased when the waveguide elements are formed by using the same wafer. Furthermore, as the element dimension is increased, the waveguide elements are made bulky and constitute an obstacle in incorporating multiple-core optical fiber connectors in optical communication systems, whereby another problem arises, by which the high concentration is hindered.
Furthermore, recently, another type of multiple-core optical connector is requested, which is able to alternately make light of different wavelengths incident into optical waveguide in the arrayed order thereof, that is, wherein when a plurality of optical waveguides are juxtaposed and formed on a waveguide element, light of wavelength .lambda.1 is made incident into waveguides of odd numbers, for example, the 1st, 3rd, 5th waveguides, etc. and light of wavelength .lambda.2 is made incident into optical waveguides of even numbers while each light of of the same wavelength is able to be collectively propagated by picking up light of wavelength .lambda.1 from optical waveguides of odd numbers and light of wavelength .lambda.2 from optical wavelengths of even numbers. However, no multiple-core optical connector having such features has been proposed before.
Therefore, in Japanese laid-open patent publication no. 246887 of 1995, the present applicant proposed a multiple-core optical connector which can be formed to be small-sized even though the number of cores of an optical fiber (optical fiber cored line) to be arrayed is large, and hopefully which can collectively propagate every light of the same kind by alternately causing different light to be made incident into a plurality of juxtaposed optical waveguides, etc. in the order of juxtaposition and alternately picking up different light from optical waveguides, etc. in the arrayed order thereof.
FIG. 24 shows a multiple-core optical connector proposed-by the applicant. As shown in the same drawing, the proposed multiple-core optical connector is composed so as to have an optical fiber tape 6 and a ferrule 2. FIG. 25 shows the construction of the ferrule 2.
Furthermore, in order to easily understand the features of the proposed optical connector, although in FIG. 24 the size of the optical fiber tape 3, etc. is exemplarily illustrated in enlargement with respect to the ferrule 2, actually as shown in FIG. 25, the width W.sub.1 of the optical fiber tape 6 is formed to be small, for example, one-third or less the width W.sub.2 of the ferrule 2. Furthermore, in FIG. 25, (a) is a bottom view of the ferrule 2, (b) is a cross-sectional view taken along the line A--A in (a), (c) is a front elevational view thereof, and (d) is a rear side view thereof.
As shown in FIG. 24, the proposed multiple-core optical connector has the first optical fiber tape 6a which is composed by juxtaposing the first four optical fiber cored lines 3a to be band-like and the second optical fiber tape 6b which is composed by juxtaposing the second four optical fiber fiber cored lines 3b to be band-like, so that the first optical fiber tape 6a and the second optical fiber tape 6b are overlapping each other. As shown in FIG. 22(a), the first bare optical fiber 4a and the second bare optical fiber 4b, the coatings of which consisting of nylon jacket 10 and primary coat 15 at the tip end of each of these optical fiber tapes 6a,6b are removed, are array-converted so as to be alternately disposed. As shown in FIG. 22(b), this array-conversion is performed by alternately disposing the first bare optical fiber 4a and the second bare optical fiber 4b with the nylon jacket 10 and primary coat 15 removed, so that the second bare optical fibers 4b are respectively inserted into each spacing (about 125 .mu.m) formed between the respective first bare optical fibers 4a.
As shown in FIG. 25, an optical fiber tape insertion portion 18 into which optical fiber tapes 6a,6b are inserted is formed to be like a horizontal hole at the rear connection end face 11 side of the ferrule 2, and an adhesive pouring port 20 is formed at the bottom side of the ferrule 2 at the tip end side of the optical fiber tape insertion portion 18. The vertical opening width of the optical fiber tape insertion portion 18 is formed so as to have an opening width corresponding to the total thickness of the thickness of the first optical fiber tape 6a and that of the second optical fiber tape 6b, so that the first optical fiber tape 6a and the second optical fiber tape 6a can be inserted therethrough in a mutually overlapped state.
A wave-like U-shaped groove in which the first and second bare optical fibers 4a,4b are disposed is formed at the tip end side of the optical fiber tape insertion portion 18, and the U-shaped groove forms an optical fiber insertion hole 13. The arraying pitch of the optical fiber insertion holes 13 is formed to be roughly coincident with the outer diameter r (r.apprxeq.125 .mu.m) of the respective bare optical fibers 4a,4b, that is, the outer diameter of the respective optical fiber cored lines 3a,3b with their coatings eliminated, wherein the optical fiber insertion holes 13 are juxtaposed in a row without any clearance.
The optical fiber tapes 6a, 6b in which the first and second bare optical fibers 4a, 4b are array-converted are inserted into the ferrule 2 as shown in FIG. 22. Accordingly, the first and second bare optical fibers 4a, 4b are alternately inserted into the optical fiber insertion holes 13 of the ferrule 2 and are arrayed in the ferrule 2 at an arraying pitch which is almost coincident with the outer diameter of the respective bare optical fibers 4a,4b, wherein the respective optical fiber tapes 6a, 6b are fixed in the optical fiber tape insertion portion 18 with an adhesive poured through the adhesive agent pouring port 20, thereby causing the proposed multiple-core optical connector to be formed.
With the proposed multiple-core optical connector, since the arraying pitch of bare optical fibers 4a, 4b at the tip end side (connection end face side) of the optical fiber tapes is formed to be an arraying pitch of a size which is roughly coincident with the outer diameter of bare optical fibers 4a, 4b, an effect can be obtained, by which a remarkably small-sized multiple optical connector can be formed in comparison with a conventional multiple-core optical connector formed by arraying eight bare optical fibers 4 at a pitch of 250 .mu.m.
Furthermore, the bare optical fibers 4a, 4b which respectively form the first optical fiber tape 6a and the second optical fiber tape 6b are array-converted to be in a row so that they are arrayed at the connection end face 5 side of the multiple-core optical connector. Therefore, for example, as shown in FIG. 24, in a case where light of wavelength .lambda.1 is made incident into each of the first optical fiber cored lines 3a of the first optical fiber tape 6a and light of wavelength .lambda.2 is made incident into the second optical fiber cored lines 3b of the second optical fiber tape 6b, both light of wavelength .lambda.1 and light of wavelength .lambda.2 are respectively caused to propagate in the first optical fiber cored lines and the second optical fiber cored lines, whereby propagation channels of the light of wavelength .lambda.1 and light of wavelength .lambda.2 are array-converted at the conversion part where the bare optical fibers 4a, 4b are array-converted. Accordingly, light of wavelength .lambda.1 outgoing from the first bare optical fibers 4a and light of wavelength .lambda.2 outgoing from the second bare optical fibers 4b are caused to outgo from the tip end side (connection end face 5 side of the multiple-core optical connector) of the bare optical fibers 4a, 4b under a condition that they are placed in a row.
Therefore, for example, if a waveguide element in which a plurality of optical waveguides are juxtaposed is connected to the connection end face 5 side of the multiple-core optical fiber, it is possible to make light of wavelength .lambda.1 and light of wavelength .lambda.2 incident into each of the juxtaposed optical waveguides in their arrayed order, that is, light of wavelength .lambda.1 can be made incident into waveguides of odd numbers, for example, the 1st, 3rd, 5th waveguides, etc. and light of wavelength .lambda.2 can be made incident into optical waveguides of even numbers.
Furthermore, to the contrary, in a case where light of wavelength .lambda.1 and light of wavelength .lambda.2 are alternately caused to outgo from the respective optical waveguides of a waveguide element, in which a plurality of optical waveguides are juxtaposed, in the arrayed order of the optical waveguides, when the waveguide element is connected to a multiple-core optical connector according to the proposed embodiment, for example, the light of wavelength .lambda.1 is made incident into the first bare optical fibers 4a, and the light of wavelength .lambda.2 is made incident into the second bare optical fibers 4b.
Accordingly, as in the above example, since the optical propagation channel is array-converted at the array-conversion part of the bare optical fibers 4a, 4b, light of wavelength .lambda.1 propagated in the first bare optical fibers 4a is collected and is caused to outgo from the first optical fiber tape 6a, and light of wavelength .lambda.2 propagated in the second bare optical fibers 4b is collected and is caused to outgo from the second optical fiber tape 6b. Thus, by using the proposed multiple-core optical connector, an effect can be obtained, by which light of different wavelengths caused to outgo from the waveguide element, etc. in an alternately juxtaposed state can be shared to the first optical fiber tape 6a side and the second optical fiber tape 6b side, and the same can be picked up.
However, since the abovementioned multiple-core optical connector proposed by the applicant is such that a plurality of optical fiber insertion holes 13 are concentrated and arrayed at a pitch roughly coincident with the outer diameter of bare optical fibers 4, the coatings of which are removed, inside the tip end side of the ferrule 2 produced by molding resin, and these optical fiber insertion holes 13 have a very small hole diameter (for example, the diameter is about 126 .mu.m) so that the bare optical fibers 4 are inserted without any play, it was very difficult to insert the bare optical fibers 4a, 4b at the tip end side into the optical fiber insertion holes 13 without any error in the array thereof after they are alternately array-converted in the correct order when the optical fiber tapes 6a, 6b, the coatings of which are removed, are overlapped and were inserted from the optical fiber tape insertion portion 18 side into the optical fiber insertion holes 13. Therefore, a problem arises in that the efficiency of assembling multiple-core optical connectors is low, and the assembling cost thereof is increased. It was disadvantageous that this problem would become remarkable in line with an increase of the number of cores of a multiple-core optical connector.
Furthermore, as described above, although it is usually performed that a multiple-core optical connector is connected to a quartz-oriented, etc. optical waveguide component (optical waveguide element), recently, a filter insertion type in which a filter is attached to an optical waveguide of the optical waveguide component has positively been developed. This is such that a plurality of waveguides of a 2.times.2 optical coupler (an optical coupler having two inputs and two outputs) as shown in FIG. 23(a) are juxtaposed and formed on a waveguide substrate, a filter 16 such as SWPF (short wave pass filter), etc. is attached to appointed ports (ports of odd numbers or even numbers) of the optical coupler, and the waveguide itself is caused to have a feature to transmit or interrupt light of a certain wavelength.
Such a filter-inserted type optical waveguide component is produced by forming a slit on a waveguide substrate, on which a waveguide is formed, in a pattern of crossing the waveguide and inserting a combtooth-like worked filter 16, shown in FIG. 23(b), into the slit.
However, since the waveguide substrate itself is very expensive and is abolished as a defective product if any trouble arises in the process of forming a slit into which the filter 16 is inserted, and inserting and fixing the filter, a problem arises, by which the production cost of waveguide components is increased, depending upon the yield ratio of these processes.